Wet layed bundled fiber mat with binder fiber

ABSTRACT

A method of producing a wet-layed non-woven mat from glass fibers includes the steps of: drawing streams of molten glass into continuous filaments, applying a size to the continuous filaments, gathering the continuous filaments into strands, chopping the strands into discrete length bundles while substantially maintaining the integrity of the bundles, drying the bundles, adding the bundles and a plurality of binder fibers to an aqueous-based mixture, thereby forming a slurry, mixing the slurry to entangle the bundles and the binder fibers, wherein the integrity of the bundles is substantially maintained in the slurry, transferring the slurry to a forming wire, wherein water is removed from the slurry to form a web while substantially maintaining the integrity of the bundles, and heating the web to fuse intersections between the bundles and the binder fibers, thereby forming a mat while substantially maintaining the integrity of the bundles.

RELATED APPLICATIONS

None.

TECHNICAL FIELD

This invention relates to fibrous glass mats and their method of manufacture. More particularly this invention relates to a wet-layed method of making a fibrous glass mat, particularly a glass mat having chopped bundles of fibers, and the mats formed by this method.

BACKGROUND OF THE INVENTION

Fibrous glass mats are used as reinforcing elements for a variety of products including roofing shingles, flooring, and wall coverings, as well as in the formation of thermoset laminate parts using polymer resins. The fiberglass mat industry uses fiberglass fibers of various lengths to make mats. These fiberglass fibers are generally coated with a sizing agent, and may include an antistatic compound, such as a cationic softener.

Two common methods for producing glass fiber mats from glass fibers involve wet-layed and dry-layed processing. Typically, in a dry-layed process, fibers are chopped and air blown onto a conveyor, and a binder is applied to form a mat. Dry-layed processes may be particularly suitable for the production of highly porous mats having bundles of glass fibers. However, dry-layed processes tend to produce mats that do not have a uniform weight or strength throughout their surface area. This is particularly true for lightweight dry-layed mats having a basis weight of 200 g/m² or less. In addition, the use of dry-chopped input fibers can be more expensive to process than those used in a wet-layed process, as the fibers in a dry-layed process are typically dried and packaged in separate steps before being chopped. The drying and packaging steps may not be necessary in wet-layed processes.

In a wet-layed process, an aqueous solution, often referred to in the art as “white water”, is formed, and the glass fibers are dispersed in the solution. The white water may contain dispersants, viscosity modifiers, defoaming agents, or other chemical agents. Chopped fibers are then introduced into the white water and agitated such that the fibers become dispersed, forming a slurry. The fibers of the slurry may then be deposited onto a moving screen, whereupon a substantial portion of the water is removed to form a web. A binder is then applied to the web and the resulting mat is dried to remove the remaining water, and the binder is cured to form the finished mat.

It would be advantageous if methods of manufacturing glass fiber mats could be improved for greater efficiency.

SUMMARY OF THE INVENTION

The above objects as well as other objects not specifically enumerated are achieved by a method of producing a wet-layed non-woven mat from glass fibers. The method comprising the steps of: drawing streams of molten glass into continuous filaments, applying a size to the continuous filaments, gathering the continuous filaments into strands, chopping the strands into discrete length bundles while substantially maintaining the integrity of the bundles, drying the bundles, adding the bundles and a plurality of binder fibers to an aqueous-based mixture, thereby forming a slurry, mixing the slurry to entangle the bundles and the binder fibers, wherein the integrity of the bundles is substantially maintained in the slurry, transferring the slurry to a forming wire, wherein water is removed from the slurry to form a web while substantially maintaining the integrity of the bundles, and heating the web to fuse intersections between the bundles and the binder fibers, thereby forming a mat while substantially maintaining the integrity of the bundles.

Various objects and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiment, when read in light of the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an enlarged schematic perspective view of a glass fiber mat comprised of glass bundles hydroentangled with binder fibers.

DETAILED DESCRIPTION OF THE INVENTION

A wet-layed fibrous glass mat 10 is shown in FIG. 1. The glass mat 10 includes glass bundles 12 and fused hydroentangled binder fibers 14.

The term hydroentangled, as used herein, is intended to include any of the processes that entangle binder fibers and glass bundles. Some examples of processes that entangle binder fibers and glass bundles include mixing in a slurry or use of water jets that are shot through the wet-layed fibrous mat.

The term glass, as used herein, is intended to include any of the glassy mineral materials, such as rock, slag and basalt, as well as traditional glasses.

The glass mat 10 is produced from a method that includes producing glass bundles 12. Processes for producing the bundles 12 are well known in the art and one of these processes will be summarized herein. A feeder is adapted to supply molten streams of material, such as glass, which are drawn into continuous filaments. A size is applied to the continuous filaments to coat the continuous filaments. Coating of the filaments with a size provides protection to the filaments from interfilament abrasion during production of the fibers, controls the filaments characteristics and aids in the handling and fabrication of additional production processes. The size can be applied by conventional methods such as by an application roller or by spraying the size directly onto the filaments. The size can be any type suitable to protect the filaments from interfilament abrasion during production of the fibers. In one embodiment, the composition of the size includes one or more film forming agents, such as for example polyurethane film former, polyester film former, and/or epoxy resin film former, at least one lubricant, and at least one silane coupling agent (such as an aminosilane or methacryloxy silane coupling agent). When needed, a weak acid such as acetic acid, boric acid, metaboric acid, succinic acid, citric acid, formic acid, and/or polyacrylic acids may be added to the size composition to assist in the hydrolysis of the silane coupling agent.

In this embodiment, the filaments are relatively straight or slightly curved glass fibers. In another embodiment, the filaments may be curled fibers or semi-curled fibers. The continuous filaments are then gathered into strands by any suitable apparatus including splitter combs or any other method sufficient to gather continuous filaments into strands. Each strand contains many filaments, such as, for example, 125 to 500 filaments.

The strands with the applied size are next chopped into bundles 12. In this embodiment, the strands with the applied size are chopped into bundles 12 while substantially maintaining the integrity of the bundles 12. Substantially maintaining the integrity of the bundles 12 is defined to mean that the bundles 12 remain substantially intact and are not dispersed as individual filaments. Substantially maintaining the integrity of the bundles 12 is important to provide increased strength to the glass mat 10 as well as providing increased strength for the final thermoset laminate. Traditional dispersed fiber wet process mats require large amounts of polymer material to form a thermoset laminate product. The large amounts of polymer materials do not have sufficient glass content to provide significant reinforcement. As will be discussed later, this embodiment allows the glass mat 10 to gain the air layed advantage of reinforcing bundles and the wet layed advantage of improved weight distribution.

The methods for chopping the strands with the applied size into bundles 12 can include any well known means including wheel cutters or any other suitable cutter sufficient to chop the strands with the applied size into bundles 12 while substantially maintaining the integrity of the bundles 12. In one embodiment, the bundles 12 have irregular and random lengths of approximately 1.25 inches. In another embodiment, the bundles 12 can be substantially the same length. In yet another embodiment, the bundles 12 can have irregular and random lengths of more than or less than 1.25 inches.

The bundles 12 with the applied size are transferred to a drying wire where the bundles 12 are dried. Any suitable means can be used to dry the bundles 12. In this embodiment, after the bundles 12 have been dried to a range of about 0% to about 0.5 wt % moisture, the chopped dry bundles 12 are packaged, such as in a box or a container, for transportation and storage, and for future use. In another embodiment, the chopped dry bundles 12 can be immediately used in a production process for reinforced mat.

The glass mats 10 are formed using wet-layed non-woven technology. The glass mat 10 is made by first adding the chopped dry bundles 12 and a plurality of binder fibers 14 to a slurry. The term binder fiber, as used herein, is intended to include fibers of a synthetic thermoplastic or thermoset polymeric material. When binder fibers 14 are subjected to their softening temperature, the binder fibers 14 will soften sufficiently to be able to fuse themselves and the bundles 12 at points of contact between the binder fibers 14 and the bundles 12. The binder fiber 14 materials can include thermoplastic polymeric materials and co-polymeric materials such as polyvinyl acetate (PVA), polyethylene terephthalate (PET), polypropylene and various types of thermoplastic polyesters.

As previously mentioned, the chopped dry bundles 12 and the binder fibers 14 are added to a slurry. The slurry can be an aqueous mixture and can have other chemical additives, such as viscosity modifiers and preliminary binders. The chopped dry bundles 12 and the binder fibers 14 are mixed in the slurry. As the chopped dry bundles 12 and the binder fibers 14 are mixed in the slurry, the chopped dry bundles and the binder fibers 14 are hydroentangled at the intersections between the chopped dry bundles 12 and the binder fibers 14. The intersections between the chopped dry bundles 12 and the binder fibers 14 are points of contact that will be fused together as will be discussed later. In this embodiment, the chopped dry bundles 12 and the binder fibers are hydroentangled in the slurry in a manner such that the integrity of the chopped dry bundles 12 is substantially maintained. As previously mentioned, substantially maintaining of the integrity of the bundles 12 substantially prevents the bundles 12 from being dispersed in the slurry as individual filaments. Substantially maintaining the integrity of the bundles 12 in the slurry provides increased strength to the glass mat 10 and improved reinforcement characteristics of the final thermoset laminate.

The slurry is formed from the combination of the aqueous mixture, the chopped dry bundles 12 and the binder fibers 14, resulting in a slurry having a high viscosity. In this embodiment, the viscosity of the slurry is greater than about 1.8 centipoises. In another embodiment, the resulting viscosity of the slurry can be in a range of from about 1.5 centipoises to about 6.0 centipoises. A high viscosity slurry is used during the hydroentanglement of the chopped dry bundles 12 and the binder fibers 14 to assist in maintaining the integrity of the chopped bundles 12. Specifically, a high viscosity slurry assists in preventing dispersion of the bundles 12, thereby resulting in a stronger glass fiber mat 10.

In another embodiment, additional individual fibers or additional bundles with a lower filament count may be added to the slurry. The additional individual fibers may be added for desired characteristics in the glass mat 10.

In this embodiment, the slurry is transferred to a first forming wire. The first forming wire is a mesh-based conveyor that can be of the type that is well known in the art. The first forming wire is adapted to receive the slurry and move the slurry to a second forming wire while removing water from the slurry. Alternatively, the first forming wire can be any structure or method of receiving the slurry and moving the slurry to additional production steps while removing water from the slurry. In this embodiment, the water is removed from the slurry by a vacuum positioned below the first forming wire. The vacuum is configured to suction water from the slurry as the slurry moves to the second forming wire. In another embodiment, the water in the slurry can be removed by any other suitable method.

In this embodiment, the slurry moves along the first forming wire and transitions to the second forming wire. The second forming wire is also a mesh-base conveyor that can be of the type that is well known in the art. The second forming wire is adapted to receive the slurry from the first forming wire and move the slurry to a drying station and a curing station. As previously discussed, the slurry includes the bundles 12, the hydroentangled binder fibers 14, and the aqueous solution. As the slurry transitions from the first forming wire to the second forming wire, the hydroentangled binder fibers 14 provide some structure and strength to the slurry which enables the slurry to bridge any gap that may exist between the first forming wire and the second forming wire.

In another embodiment, the slurry remains on the first forming wire and the first forming wire moves the slurry to a drying and a curing station. The drying and curing station includes an oven wire. The slurry moves from the first forming wire to the oven wire. Alternatively, the slurry can be moved on any combination of forming wires, oven wires or any structure or method sufficient to receive the slurry and moving the slurry to additional production steps while removing water from the slurry.

At the drying station, any remaining water is removed from the slurry according to any suitable process. The remaining aqueous solution including the bundles 12 and the hydroentangled binder fibers 14 form a web. The web is moved by the second forming wire to a curing station. The curing station heats the web to drive off the remaining water and to cure the binder fibers. Heating of the web causes the hydroentangled binder fibers 14 to fuse to the bundles 12 at each intersection thereby helping to bond the mat together. Fusing of the hydroentangled binder fibers 14 to the bundles 12 is completed in a manner such that the integrity of the bundles 12 is substantially maintained resulting in a stronger glass mat 10. In this embodiment, the web is subjected to a temperature in a range of approximately 300° F. to approximately 450° F. for a period of time in a range of about 60 seconds to about 90 seconds. In another embodiment, the web can be subjected to temperatures more than 450° F. or less than 300° F. and for periods of time more than 90 seconds or less than 60 seconds. In yet another embodiment, the web can be cured in any other suitable manner sufficient to cause the hydroentangled binder fibers 14 to fuse to the bundles 12.

The following examples are representative, but are in no way limiting as to the scope of this invention.

EXAMPLES Example 1 Composition of the Slurry

An experimental process was carried out to form a slurry by combining a white water solution with a quantity of bundles 12, formed by chopping an amount of filaments as described above, and a quantity of binder fibers. The white water solution is formed by a combination of materials as shown in Table 1.0.

TABLE 1.0 Material Quantity (wt %) Polymer Film Former 5.942% Silane 0.079% Amino Silane 0.332% Film Former 0.707% Cationic Lube 0.037% Nonionic Lube 0.296% Water 92.600% 

Example 2 Alternate Composition of the Slurry

Another experimental process was carried out to form a slurry by combining a white water solution with a quantity of bundles 12, formed by chopping an amount of filaments as described above, and a quantity of binder fibers. The white water solution is formed by a combination of materials as shown in Table 2.0.

TABLE 2.0 Material Quantity (wt %) Viscosity Modifier 0.05–4.00% Antifoam 1.00–5.00% Dispersing Agent  2.00–10.00% Water 81.00–97.00%

Example 3 Forming the Mat

Using the slurry formed in Example 1 or Example 2, the slurry was transferred to a first forming wire. The flow of the slurry onto the first forming wire is regulated to form a base web or mat having a basis weight of 1.0 oz/ft² at a line speed of 15 ft/min. Excess moisture is removed by a vacuum process. No additional binder is applied to the web on the first forming wire. The web transitions to a second forming wire also having a line speed of 15 ft/min. While moving on the second forming wire, the web is further dried by a vacuum process. After drying and while still moving, the web is cured by heating in a continuous oven. While moving within the oven, the web is subjected to a temperature in a range of approximately 300° F. to approximately 450° F. for a period of time in a range of about 60 seconds to about 90 seconds. No additional binder is applied to the web while the web is moving on the second forming wire. The resulting non-woven glass mat 10 is suitable for use as a substrate for a variety of products including roofing shingles, flooring, automotive panels and wall coverings, as well as in the formation of thermoset laminate parts using polymer resins.

Example 4 Testing the Tensile Strength of the Mat

The glass mat 10 formed in Examples 1-3 exhibited superior tensile strength compared to control samples and commercial samples. The superior tensile strength of the glass mat 10 was exhibited in both the machine direction and the cross machine direction.

Testing the tensile strength of the glass mat 10 involved determining the breaking strength of the glass mat 10 in both the machine direction and the cross machine direction. The breaking strength of the glass mat 10 was determined by a testing process using a glass mat 10 specimen, approximately 2 inches wide and 10 inches long. The specimen is clamped in a Constant Rate of Extension Tensile Tester (CRE) using pneumatic, flat-faced clamps. Examples of constant rate of extension tensile testers include the constant rate of extension tensile tester manufactured by Instron Corporation in Norwood, Mass. or Thwing Albert Instrument Company of West Berlin, N.J. Any other equivalent tester can be used. The glass mat 10 test specimen are prepared by cutting the glass mat 10 into approximately 2 inch wide by 10 inch long pieces. Specimen are prepared for both the machine direction and the cross machine direction. Although not necessary, the mats were conditioned for testing in test conditions of 73±4° F. and 50±5% relative humidity. The specimen were tested at a specimen rate of 50±2 mm/minute. The force required to break the specimen was recorded by automated recording devices. A quantity of five specimen were tested for both the machine direction and the cross machine direction.

Example 5 The Tensile Strength of the Mat

Using the glass mat 10 prepared in Examples 1-3, and the testing method of Example 4, the glass mat 10 exhibited superior tensile strength compared to control samples and commercial samples. The superior tensile strength is attributable to excellent bundle integrity and fusion of the polymeric binder fibers. It is to be appreciated that glass mats having different basis weights will exhibit different tensile strengths. The tensile strength testing results are shown Table 3.0.

TABLE 3.0 Machine Cross Direction Machine Direction Basis Tensile Tensile Weight Strength Standard Strength Standard Binder Fiber Mats Oz/ft{circumflex over ( )}2 Lbs Deviation Lbs Deviation Control w/Emulsion 1.08 14.6 3.4 5.9 0.5 Binder 11% PVA Fiber 0.98 61.3 5.3 24.3 2.5  5% PVA Fiber 1.25 44.8 2.3 40.8 1.4  6% PET-PET Fiber 0.48 23.8 2.5 13.7 1.1  5% PET-PET Fiber 1.33 24.5 1.5 10.5 0.8 723A OC 1.0 9.8 3.2 9.5 2.4 Commercial M705 OC 1.0 10.7 3.1 8.4 1.3 Commercial

The principle and method of production of this glass mat have been described in its preferred embodiments. However, it should be noted that the glass mat may be produced otherwise than as specifically illustrated and described without departing from its scope. 

1. A method of producing a wet-layed non-woven mat from glass fibers, the method comprising the steps of: drawing streams of molten glass into continuous filaments; applying a size to the continuous filaments; gathering the continuous filaments into strands; chopping the strands into discrete length bundles while substantially maintaining the integrity of the bundles; drying the bundles; adding the bundles and a plurality of binder fibers to an aqueous-based mixture, thereby forming a slurry, mixing the slurry to entangle the bundles and the binder fibers, wherein the integrity of the bundles is substantially maintained in the slurry; transferring the slurry to a forming wire, wherein water is removed from the slurry to form a web while substantially maintaining the integrity of the bundles; heating the web to fuse intersections between the bundles and the binder fibers, thereby forming a mat while substantially maintaining the integrity of the bundles.
 2. The method of claim 1 in which the dried bundles are packaged in a container prior to their introduction to the slurry.
 3. The method of claim 1 in which individual fibers are added to the slurry.
 4. The method of claim 1 in which the glass bundles have irregular and random lengths.
 5. The method of claim 1 in which the binder fibers have irregular and random lengths.
 6. The method of claim 1 in which the slurry has a viscosity in a range from about 1.5 centipoises to about 6.0 centipoises.
 7. The method of claim 1 in which the binder fiber is one or more of the group consisting of polyvinyl acetate (PVA), polyethylene terephthalate (PET), polypropylene and thermoplastic polyesters.
 8. The method of claim 1 in which the mat has a basis weight in a range of about 0.25 to about 1.30 Oz/ft², wherein the mat has a machine direction tensile strength in a range from about 10.0 lbs to about 70.0 lbs.
 9. The method of claim 8 in which the mat has a basis weight in a range of about 0.25 to about 1.30 Oz/ft², wherein the mat has a cross machine direction tensile strength in a range from about 5.0 lbs to about 50.0 lbs. 